HC-5524 查看數據表（PDF） - Harris Semiconductor
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HC-5524 Datasheet PDF : 12 Pages
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HC-5524
Pin Descriptions (Continued)
DIP/SO
IC
PLCC
7
11
8
12
9
13
10
17
11
18
12
19
13
20
14
22
15
24
16
25
17
27
18
31
19
32
20
33
21
34
22
35
23
36
24
37
25
38
NA
39
26
41
SYMBOL
DESCRIPTION
SHD Switch Hook Detection - An active low LS TTL compatible logic output. A line supervisory output.
GKD Ground Key Detection - An active low LS TTL compatible logic output. A line supervisory output.
TST
A TTL logic input. A low on this pin will set a latch and keep the SLIC in a power down mode until the
proper F1, F0 state is set and will keep ALM low. See Truth Table on front page.
ALM
A LS TTL compatible active low output which responds to the thermal detector circuit when a safe
operating die temperature has been exceeded. When TST is forced low by an external control signal,
ALM is latched low until the proper F1, F0 state and TST input is brought high. The ALM can be tied
directly to the TST pin to power down the part when a thermal fault is detected and then reset with F0,
F1. See Truth Table on front page. It is possible to ignore transient thermal overload conditions in the
SLIC by delaying the response to the TST pin from the ALM. Care must be exercised in attempting this
as continued thermal overstress may reduce component life.
ILIMIT
Loop Current Limit - Voltage on this pin sets the short loop current limiting conditions using a resistive
voltage divider.
OUT1 The analog output of the spare operational amplifier.
-IN1
The inverting analog input of the spare operational amplifier.
TIP
An analog input connected to the TIP (more positive) side of the subscriber loop through a feed resistor
and ring relay contact. Functions with the RING terminal to receive voice signals from the telephone and
for loop monitoring purposes.
RING
An analog input connected to the RING (more negative) side of the subscriber loop through a feed resis-
tor. Functions with the TIP terminal to receive voice signals from the telephone and for loop monitoring
purposes.
RFS
Ring Feed Sense - Senses RING side of the loop for Ground Key Detection. During Ring injected ringing
the ring signal at this node is isolated from RF via the ring relay. For Tip injected ringing, the RF and RFS
pins must be shorted.
VRX
Receive Input, 4-Wire Side - A high impedance analog input. AC signals appearing at this input drive the
Tip Feed and Ring Feed amplifiers differentially.
C2
Capacitor #2 - An external capacitor to be connected between this terminal and ground. It prevents false
ring trip detection from occurring when longitudinal currents are induced onto the subscriber loop from
power lines and other noise sources. This capacitor should be nonpolarized.
VTX
Transmit Output, 4-Wire Side - A low impedance analog output which represents the differential voltage
across TIP and RING. Transhybrid balancing must be performed beyond this output to completely imple-
ment two to four wire conversion. This output is referenced to analog ground. Since the DC level of this
output varies with loop current, capacitive coupling to the next stage is necessary.
PRI
A TTL compatible input used to control PR. PRI active High = PR active low.
PR
An active low open collector output. Can be used to drive a Polarity Reversal Relay.
DG
Digital Ground - To be connected to zero potential. Serves as a reference for all digital inputs and outputs
(Note 4) on the SLIC.
RD
Ring Relay Driver - An active low open collector output. Used to drive a relay that switches ringing signals
onto the 2-Wire line.
VFB
(Note 5)
Feedback input to the tip feed amplifier; may be used in conjunction with transmit output signal and the
spare op-amp to accommodate 2-Wire line impedance matching. (This is not used in the typical applica-
tions circuit).
TF2
Tip Feed - A low impedance analog output connected to the TIP terminal through a feed resistor. Func-
tions with the RF terminal to provide loop current, and to feed voice signals to the telephone set and to
sink longitudinal currents. Must be tied to TF1.
TF1
Tie directly to TF2 in the PLCC application.
RF1
Ring Feed - A low impedance analog output connected to the RING terminal through a feed resistor.
Functions with the TF terminal to provide loop current, feed voice signals to the telephone set, and to
sink longitudinal currents. Tie directly to RF2.
5
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